Bis-(1(2)H-tetrazol-5-yl)-amine monohydrate of the formula also known as BTA having the structural formula (I), useful as a gas generant. According to the available literature, it is prepared by the reaction of sodium dicynamide with sodium azide in the presence of inorganic or organic acids.
In the patent U.S. 2003/0060634, described this reaction in the presence of hydrochloric acid (HCl), sulphuric acid (H2SO4), phosphoric acid (H3PO4), nitric acid (HNO3), perchloric acid (HClO4) and the mixtures thereof. Also some organic acids like trifluoro acetic acid, trifluoromethane sulfonic acid and methane sulfonic acid. But this patent preferred hydrochloric acid and the most preferred the addition of 1.6 molar hydrochloric acid solutions at refluxing temperature, over the course of 24 hours with 85.6% yield. But due to the formation of very fine amorphous product, it is difficult to filter the product during the scale up process.
In the patent U.S. 2008/0207914 mentioned the addition of concentrated hydrochloric acid at 60° C. for a period of 10-42 hour followed by reflux for another 24 hour yielded 86-92% with 99.4% purity by HPLC.
In the patent U.S. 2010/0261912 described the preparation of bis-(1(2)H-tetrazol-5-yl)-amine monohydrate by using boric acid, 63% sulphuric acid and 90% acetic acid. The addition was done for a period of 3 hour followed by maintenance of 10 to 42 hour.